在LINQ中返回null而不是默认值
我有LINQ查询，该查询必须检索一些DateTime值.我没有匹配的某些主题，我必须为该DateTime值返回NULL，而不是DateTime的默认值.
I have LINQ query which has to retreive some DateTime value. Somethimes I don't have match for and I have to return NULL for that DateTime value instead default value for DateTime.
如何避免这种情况并返回NULL而不是默认值?
How can I avoid that and return NULL instead defaul value?
我的LINQ:
CreatedDate = ctaMatch.Select(d => d.CreatedDate).DefaultIfEmpty().FirstOrDefault()
在DefaultIfEmpty中，我只能放置DateTime.
In DefaultIfEmpty I can put only DateTime.
将其投射到DateTime?，这将导致DefaultIfEmpty创建一个默认集合，如果该集合为空，则该集合将包含空值.
Cast it to DateTime? that will cause DefaultIfEmpty creates a default collection that contains null value if the collection is empty.
CreatedDate = ctaMatch
.Select(d => (DateTime?)d.CreatedDate)
.DefaultIfEmpty()
.FirstOrDefault()
PS:可以省略DefaultIfEmpty，因为它后面是FirstOrDefault.
PS: The DefaultIfEmpty can be omitted, because it's followed by FirstOrDefault.